DTC P0420: 1/1 Catalytic Converter Efficiency: Description

NOTE: 1/1 HO2S may also be referred to as an upstream oxygen sensor. 1/1 HO2S is located in outlet flange of right exhaust manifold. 1/1 catalytic converter is located in right exhaust pipe.

Catalytic converter efficiency is monitored after engine warms up to 147°F (63.8°C), throttle has been open for 180 seconds at vehicle speed more than 20 MPH, with engine speed at 1200-1700 RPM and MAP vacuum 15-21 in. Hg. DTC will set in Powertrain Control Module (PCM) memory when PCM senses catalyst efficiency deteriorated to a predetermined value. Possible causes for DTC to set are: exhaust leak, engine mechanical problem, defective 1/1 catalytic converter or upstream Heated Oxygen Sensor (HO2S) is older than downstream HO2S.